The need to use the extensive coal resources in this country as a source of fuel gas is now quite evident in view of the rapid depletion of other sources. Accordingly, it has become essential to develop processes for the economic production of fuel gas for industrial uses from coal.
Atmospheric coal gasification processes are well known and well developed. Typical of these proven processes are the Koppers-Totzek, Winkler, Wellman-Galusha, Woodall-Duckman, and others. The gas produced from these gasification processes is a low Btu gas comprising a mixture of carbon monoxide and hydrogen. This gas mixture has a low fuel value of about 300 Btu/ft.sup.3 or less, on the average, which is too low for most industrial uses.
The fuel value of the gas produced by the atmospheric coal gasification processes can be enhanced with the use of high temperatures and pressures, sometimes accompanied by the use of oxygen and/or catalysts, to make the hydrogen and carbon monoxide present react to produce methane. Methane has a heat of combustion of 1013 Btu/ft.sup.3, whereas carbon monoxide and hydrogen have Btu's of about 322 and 325, respectively. The chief disadvantage, of course, of these procedures for enhancing the fuel value of the low Btu gas is the expense involved. The expense is so great that low Btu gas enhanced in this manner is not competitive with other fuels available for industrial uses.
So-called intermediate Btu gas is suitable for industrial uses, this gas having a Btu value of 450 Btu/ft.sup.3 or more. It will burn well in existing gas burner equipment in power plants and other industrial applications with only minor modification in the burner head. The Btu value is high enough so that its use does not result in loss of boiler efficiency and, further, this gas can be economically piped moderate distances, which is not true for low Btu gas.
Accordingly, it is an object of this invention to provide a relatively inexpensive process for enhancing the fuel value of the low Btu gas produced by coal gasification processes.